Add another exception for the exclusion for pip. Fixes #2993.

_distutils_hack/__init__.py

@@ -116,6 +116,8 @@ def spec_for_pip(self):
         """
         if self.pip_imported_during_build():
             return
+        if self.is_get_pip():
+            return
         clear_distutils()
         self.spec_for_distutils = lambda: None
 
@@ -130,6 +132,14 @@ def pip_imported_during_build(cls):
             for frame, line in traceback.walk_stack(None)
         )
 
+    @classmethod
+    def is_get_pip(cls):
+        """
+        Detect if get-pip is being invoked. Ref #2993.
+        """
+        import __main__
+        return os.path.basename(__main__.__file__) == 'get-pip.py'
+
     @staticmethod
     def frame_file_is_setup(frame):
         """

changelog.d/2993.change.rst

@@ -0,0 +1 @@
+In _distutils_hack, bypass the distutils exception for pip when get-pip is being invoked, because it imports setuptools.